"suru" is the right verb -- even though it is usually said to be equivalent to English "to be", it actually comes closer to "to do".

However, you left out "nani" -- Kinyoubi ni nani wo shimasu ka?
Means "What are you doing Friday". Strikes me as rather, um, intrusive. The suggestion

>kinyoubi ni naniKA (youji ga) arimasu ka?
seems more natural.

However,
>Kinyoubi ni nani ga arimasu ka.
is very odd -- what will there be on Friday? "aru" means to exist, so you are asking about some inanimate object that will exist on Friday. Maybe if you are asking, for instance, what the sushi special will be at a restaurant and the context is already established? In any case, this doesn't mean what you want it to.

And
>kinyoubi ni nani o arimasu ka
.... is just wrong. "aru" never takes wo, because it isn't a transitive verb.

(In general, it is well worth memorizing verbs WITH the appropriate particle, or as part of a pattern. One common pattern: N ga aru = there is or are N(s). TEEBURU no ue ni hon ga aru = there are books on the table.

N ga iru -- same meaning, but for living, moving things: TEEBURU ni neko ga iru. There is a cat on the table.)

HTH!

Shira

"Give me a fruitful error any time, full of seeds, bursting with its own corrections. You can keep your sterile truth for yourself." -- Vilfredo Pareto

>Also aru does not have to be for a tangible object. It is also used to talk >about events that will take place.

True, thank you for pointing that out. Apparently, in the Japanese mind, ideas, things that will happen and other immaterial "objects" are in the same category as material inanimate objects. This is also reflected in the use of "koto" to refer to such things, while "mono" refers to people and material objects. (Actually, two kanji are used, one for people and one for things, both pronounced "mono".)

"Give me a fruitful error any time, full of seeds, bursting with its own corrections. You can keep your sterile truth for yourself." -- Vilfredo Pareto